1. The Field of the Invention
The present invention is related to a nozzle for use on a decoy flare. More particularly, the present invention is related to a nozzle positioned off-axis to increase the effective cross-sectional area of the plume of a decoy flare as a function of aspect angle.
2. Technical Background
Decoy flares are used defensively by combat aircraft to evade heat-seeking missiles directed at such aircraft by an enemy. At an appropriate time after the enemy launches a heat-seeking missile, the targeted aircraft releases a decoy flare. The decoy flare burns in a manner that simulates the engines of the targeted aircraft. Ideally, the missile locks onto and pursues the decoy, permitting the targeted aircraft to escape unharmed.
Early decoy techniques utilized bundles of chaff, i.e., strips of metal which would reflect radar energy to counter radar guided missiles. The chaff bundles were housed in square or rectangular shaped cartridges which were held in correspondingly shaped dispensers on the aircraft.
However, the advancement of missile technology has resulted in the development of missiles which examine a potential target's energy spectrum in order to distinguish decoys from targeted aircraft using infrared wavelength signatures. Typical of such missiles are missiles which target an infrared light source.
The burn requirements of the decoy flare must therefore be determined by reference to the known characteristics of the targeted aircraft's engine emissions as interpreted by the heat-seeking missile. It is necessary for the decoy to emit light in the infrared (IR) spectrum and for a duration that will induce the missile to lock onto the decoy instead of the escaping aircraft.
One problem which has been encountered in the development of suitable IR decoy flares is the difficulty of achieving a sufficiently large plume by the decoy flare. Of course, as the cross-sectional area of the plume of the decoy flare is increased, the likelihood that the missile will lock onto the decoy flare, instead of the target aircraft, also increases.
One proposed solution for achieving a larger plume area is to utilize larger flares. This solution is problematic because the design envelope of the flare is preferably limited by that which can be contained within a chaff dispenser cartridge. Also, increasing the size of the decoy flare increases the airplane payload due to flares which may ultimately result in a reduction in the number of flares which can be carried.
Another challenge facing flare designers is the difficulty of designing a flare which is stable in flight. Because chaff dispenser cartridges are rectangular in cross section, maximization of this available area has resulted in flares which are also rectangular in cross section. Such geometries do not lend easily themselves to stable flight.
From the foregoing, it will be appreciated that it would be an advancement in the art to provide a decoy flare which is capable of emitting a combustion plume having a greater cross-sectional area without increasing the physical dimensions or weight of the flare, thereby permitting the flare to be used with presently existing chaff dispensers without increasing the payload of the aircraft from which the flare is to be launched.
It would be a further advancement in the art to provide such a flare which had a rectangular cross section, thereby enabling it to maximize the available area within a chaff dispenser cartridge, yet which would be stable in flight.
Such a device is disclosed and claimed herein.